b564111aff
This commit fixes an off-by-one error which is only manifested by the new behavior of OP_CODESEPARATOR within sig hashes triggered by the segwit behavior. The current behavior within the Script VM (txscript.Engine) is known to be fully correct to the extent that it has been verified. However, once segwit activates a consensus divergence would emerge due to *when* the program counter was incremented in the previous code (pre-this-commit). Currently (pre-segwit) when calculating the pre-image to a transaction sighash for signature verification, *all* instances of OP_CODESEPARATOR are removed from the subScript being signed before generating the final sighash. SegWit has additional nerfed the behavior of OP_CODESEPARATOR by no longer removing them (and starting after the last instance), but instead simply starting the subScript to be directly *after* the last instance of an OP_CODESEPARATOR within the pkScript. Due to this new behavior, without this commit, an off-by-one error (which only matters post-segwit), would cause txscript to generate an incorrect subScript since the instance of OP_CODESEPARATOR would remain as part of the subScript instead of being sliced off as the new behavior dictates. The off-by-one error itself is manifested due to a slight divergence in txscript.Engine’s logic compared to Bitcoin Core. In Bitcoin Core script verification is as follows: first the next op-code is fetched, then program counter is incremented, and finally the op-code itself is executed. Before this commit, btcd flipped the order of the last two steps, executing the op-code *before* the program counter was incremented. This commit fixes the post-segwit consensus divergence by incrementing the program-counter *before* the next op-code is executed. It is important to note that this divergence is only significant post-segwit, meaning that txscript.Engine is still consensus compliant independent of this commit. |
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|---|---|---|
| .. | ||
| data | ||
| consensus.go | ||
| doc.go | ||
| engine.go | ||
| engine_test.go | ||
| error.go | ||
| error_test.go | ||
| example_test.go | ||
| hashcache.go | ||
| hashcache_test.go | ||
| log.go | ||
| opcode.go | ||
| opcode_test.go | ||
| README.md | ||
| reference_test.go | ||
| script.go | ||
| script_test.go | ||
| scriptbuilder.go | ||
| scriptbuilder_test.go | ||
| scriptnum.go | ||
| scriptnum_test.go | ||
| sigcache.go | ||
| sigcache_test.go | ||
| sign.go | ||
| sign_test.go | ||
| stack.go | ||
| stack_test.go | ||
| standard.go | ||
| standard_test.go | ||
txscript
Package txscript implements the bitcoin transaction script language. There is a comprehensive test suite.
This package has intentionally been designed so it can be used as a standalone package for any projects needing to use or validate bitcoin transaction scripts.
Bitcoin Scripts
Bitcoin provides a stack-based, FORTH-like language for the scripts in the bitcoin transactions. This language is not turing complete although it is still fairly powerful. A description of the language can be found at https://en.bitcoin.it/wiki/Script
Installation and Updating
$ go get -u github.com/btcsuite/btcd/txscript
Examples
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Standard Pay-to-pubkey-hash Script
Demonstrates creating a script which pays to a bitcoin address. It also prints the created script hex and uses the DisasmString function to display the disassembled script. -
Extracting Details from Standard Scripts
Demonstrates extracting information from a standard public key script. -
Manually Signing a Transaction Output
Demonstrates manually creating and signing a redeem transaction.
GPG Verification Key
All official release tags are signed by Conformal so users can ensure the code has not been tampered with and is coming from the btcsuite developers. To verify the signature perform the following:
-
Download the public key from the Conformal website at https://opensource.conformal.com/GIT-GPG-KEY-conformal.txt
-
Import the public key into your GPG keyring:
gpg --import GIT-GPG-KEY-conformal.txt -
Verify the release tag with the following command where
TAG_NAMEis a placeholder for the specific tag:git tag -v TAG_NAME
License
Package txscript is licensed under the copyfree ISC License.